Polyphenylene ether resin or a blend of polyphenylene ether and polystyrene is excellent in mechanical and electrical properties at relatively higher temperatures. Accordingly, the resins are suitable for a wide range of applications such as automobile parts and electrical and electronic parts. However, the polyphenylene ether resin or a blend thereof has a defect in that it is poor in molding processability, impact resistance and resistance to oil and other chemicals.
Polyamide resin has been used as engineering plastics for various applications, as the resin provides superior chemical resistance and processability in a molding process. However, the applications of polyamide resin are often limited by its poor resistances to heat or impact.
Therefore, in order to remove the defects of the polyphenylene ether and polyamide resin and to maintain the favorable properties of them, numerous researches have been carried out in this area.
A resin composition consisting of (A) a polyphenylene oxide and (B) a polyamide of 0.1 to 25% by weight of the total composition is disclosed and claimed in U.S. Pat. No. 3,379,792. However if the polyamide is in excess of 20% by weight of the total composition, phase separation between the components dominates and leads to poor physical properties of molded articles.
U.S. Pat. No. 4,315,086 discloses a resin composition comprising 5 to 95% by weight of a polyphenylene oxide and 95 to 5% by weight of a polyamide and 0.01 to 30 parts by weight of an ingredient selected from the group consisting of (A) liquid diene polymers, (B) epoxy compounds and (C) compounds having both of (a) a carbon--carbon double or triple bond and (b) a carboxylic acid, acid anhydride, acid amide, imide, carboxylic acid ester, amino or hydroxyl group per 100 parts by weight of the total of polyphenylene oxide and polyamide.
European Patent Publication No. 046,040 discloses a thermoplastic resin composition having high oil-resistance which comprises (A) a polyphenylene ether resin, (B) a copolymer comprising units of a vinyl aromatic compound and an .alpha.,.beta.-unsaturated dicarboxylic acid anhydride or a copolymer comprising units of a vinyl aromatic compound and an imide compound of an .alpha.,.beta.-unsaturated dicarboxylic acid, and (C) a polyamide and optionally (D) a synthetic resinous impact modifier.
PCT International Publication No. WO 87/00540 discloses a method for functionalizing a polyphenylene ether, in which said polyphenylene ether is melt blended, in the absence of free radical initiators, with at least one functionalizing compound having at least one carbon--carbon double or triple bond and at least one carboxylic acid, acid anhydride, acid amide, imide ester, amino or hydroxyl group.
The resin composition containing the above mentioned modified polyphenylene ether has a defect of deteriorating the natural color of the resin during extrusion.
Accordingly the inventors of the present invention have developed a resin composition comprising a polyphenylene ether, a polyamide, a functionalized aromatic vinyl graft copolymer and a synthetic resinous impact modifier, which can provide a good compatibility of the polyphenylene ether and polyamide, and stable natural color during extrusion.